<template>
  <div>
    <router-link
      tag="div"
      to="/"
      class="header-abs"
      v-show="showAbs"
    >
        <span class="iconfont header-abs-back">&#xe624;</span>
    </router-link>
    <div
      class="header-fixed"
      v-show="!showAbs"
      :style="opacityStyle"
    >
        <router-link to="/">
            <div class="iconfont header-fixed-back">&#xe624;</div>
        </router-link>
        景点详情
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = { opacity }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  activated () { // 页面展示的时候绑定这个事件
    window.addEventListener('scroll', this.handleScroll)
  },
  deactivated () { // 当页面即将替换成新的页面的时候(页面被替换了以后方法解绑)
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style scoped>
   .header-abs{
       position: absolute;
       left: .2rem;
       top:.2rem;
       width: .8rem;
       height: .8rem;
       line-height: .8rem;
       border-radius: .4rem;
       text-align: center;
       background: rgba(0,0,0,.8)
   }
   .header-abs-back{
       color: #fff;
       font-size: .4rem;
   }
   .header-fixed{
        z-index: 2;
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        height: .86rem;
        line-height:.86rem;
        text-align: center;
        color: #fff;
        background: #00bcd4;
        font-size:.32rem;
    }
    .header-fixed-back{
        position: absolute;
        top: 0;
        left: 0;
        width: .64rem;
        text-align: center;
        font-size:.4rem;
        color: #fff;
    }
</style>
